I don't think it's available on the UK portal as I'm not familiar with that camera, but the latest firmware can be downloaded at the bottom of this page:
But, It was not so easy. I downloaded the file "Firmware__V5.7.20_221109_S3000464265.zip", opened it and got a folder Firmware__V5.7.20_221109_S3000464265 - and inside it a file named digicap.dav. (The zip file used 97134 KB.)
Tried to upgrade firmware with it, but it is rejected as "wrong format".
It is vital that you keep the firmware of your Hikvision devices up-to-date, which means installing the newest version as soon as it becomes available. The best and easiest way to do this is to use the device’s web browser interface. The below steps will show you where to find the newest...
Yes that's done, but I got
"The type of upgrade file mismatches. " The filename digicap.dav as in the guide.
I now will try to get the upgrade file as in the guide, not as done from bottom at the cameras spesifications. DS-2CD3B86G2T-IZHSY which seems to be wrong.
Found HIKVISION UK PORTAL
where my old firmware seems to be quite up to date. (And quite different from the file I first tried).
Therefore I close down this query. Thanks a lot for all help.
Apologies, I directed you to the firmware for the newer G5 version of that camera, the folder you've found above is correct (V5.5.802 is the latest release)!